Cytology is a branch of biology dealing with the study of the formation, structure, and function of cells. As applied in a laboratory setting, cytologists, cytotechnologists, and other medical professionals make medical diagnoses of a patient's condition based on visual examination of a specimen of the patient's cells. A typical cytological technique is a “pap” test, in which cells are scraped from a woman's cervix and analyzed in order to detect the presence of abnormal cells, a precursor to the onset of cervical cancer. Cytological techniques are also used to detect abnormal cells and disease in other parts of the human body.
Cytological techniques are widely employed because collection of cell samples for analysis is generally less invasive than traditional surgical pathological procedures such as tissue extraction biopsies. Cell samples may be obtained from the patient by a variety of techniques including, for example, by scraping or swabbing an area, or by using a needle to aspirate body fluids from the chest cavity, bladder, spinal canal, or other appropriate area. The cell samples are placed in solution and subsequently collected and transferred to a glass slide for viewing under magnification. Fixative and staining solutions may be applied to the cells on the glass slide for preserving the specimen for archival purposes and for facilitating examination.
It is generally desirable that the cells on the slide have a proper spatial distribution, so that individual cells can be examined. A single layer of cells is typically preferred. Accordingly, preparing a specimen from a fluid sample containing many cells typically requires that the cells first be separated from each other by mechanical dispersion, fluidic shear, or other techniques so that a thin, monolayer of cells can be collected and deposited on the slide. In this manner, the cytotechnologist can more readily discern abnormal cells. The cells in the monolayer are also able to be counted to ensure that an adequate number of cells have been evaluated.
Certain methods and apparatus for generating a thin monolayer of cells on a slide advantageous for visual examination are disclosed in U.S. Pat. Nos. 5,143,627, 5,240,606, 5,269,918, 5,282,978, 6,572,824, 6,562,299 and 7,579,190, all of which are assigned to the assignee of the present invention, and all of the disclosures of which are incorporated herein by reference in their entirety.
According to one method disclosed in these patents, a patient's cells in a preservative fluid in a sample container are dispersed using a spinning filter device disposed therein. A controlled vacuum is applied to the filter device to draw the fluid through a membrane thereof, until a desired quantity and spatial distribution of cells is collected against the filter. Thereafter, the filter is removed from the sample container and the filter membrane impressed against a glass slide to transfer the particles of interest to the slide in substantially the same spatial distribution as they were collected on the filter membrane.
Once a specimen is prepared, fixed, and stained, the specimen may be manually visually inspected by a cytotechnologist, typically under magnification, and with or without various sources of illumination. Alternatively or additionally, automated machine vision systems have been adapted to aid cytological inspection. For example, an automated vision system may perform a preliminary assessment of the entire slide on which the specimen is disposed to alert the cytotechnologist to potentially the most relevant areas of the slide for close inspection, or may be used to rescreen specimens already analyzed by the cytotechnologist.
The ThinPrep® 2000, ThinPrep® 3000, and ThinPrep® 5000 systems (collectively, “ThinPrep® system”), manufactured and sold by Hologic, Inc. (“Hologic”—formerly Cytyc Corporation), located in Marlborough, Mass., are effective and widely used cervical cancer screening tools available to women. Since the introduction of the ThinPrep® system in 1996, invasive cervical cancers in the US have declined. However, there remains an ongoing need for cervical screening. While the application of warm water on the collection speculum has the least risk to the quality of a collected Pap sample, many clinicians still employ the use of a lubricant gel on the speculum to ease patient discomfort during a pelvic exam. Unfortunately, the use of such lubricants during sample collection for the ThinPrep® Pap test, particularly lubricants having carbomer-based formulations, may adversely affect specimen slide adequacy, and can elevate “Unsatisfactory for Evaluation” (hereinafter “UNSAT”) rates for laboratories.